Although a large number of cancer cells develop everyday in vivo, these cancer cells are eliminated in many cases owing to the system for eliminating abnormal cells and the immune system. This prediction that cancer cells are eliminated by the immune system is supported by the fact that the incidence of cancer increases with the depression of the immune function caused by aging, an immunological disease such as AIDS or the administration of an immunosuppressive agent. From this viewpoint, immunotherapy for eradicating cancer through immunopotentiation has attracted public attention in recent years. However, the currently available immunotherapeutic methods for cancer frequently fail to induce immunity against cancer and thus efficacious treatments cannot be conducted thereby.
It is known that dendritic cells play an important role in inducing the immunity against cancer. We have already found out that MIP-1α or its functional derivative is capable of topically accumulating dendritic cells at an inflammation site or a cancer site. We have further found out that MIP-1α or its functional derivative can mobilize dendritic cell precursors several ten-fold in the blood (Yoneyama H. et al., J. Exp. Med., Vol. 193 (1), pp. 35-49 (2001); and Zhang Y. et al., J. Natl. Cancer Inst., Vol. 96, pp. 201-209 (2004)). Also, it is reported that the topical MIP-1α expression at an immune site of an immune-induced mouse results in the accumulation of dendritic cells and an antigen-specific immunity is thus induced (McKay P F et al., Eur. J. Immunol., Vol. 34, pp. 1011-1020 (2004)).
To inhibit the proliferation and metastasis of cancer cells, radiation therapy has been utilized in combination with surgery, chemotherapy, hormonal therapy and so on. However, it is difficult to completely eliminate cancer cells and, moreover, there arise some side effects such as the suppression of the immune system, a loss of appetite, anemia, a decrease in leukocytes and a decrease in platelets. Although these side effects can be relieved by stereotactic irradiation with an electron beam whereby a cancer tissue is topically treated, cancer cells can be hardly eradicated thereby. Accordingly, it has been required to develop a technique for improving and potentiating the inflammation that have been introduced into a cancer tissue by the electron beam irradiation or the functions of T cells and dendritic cells specific to cancer cells.
It is well known that the phenomenon of cancer metastasis is the most important factor in determining the prognosis of a cancer patient. However, the mechanism of “metastasis” still remains unsolved and no efficacious therapeutic method therefor has been established so far. There have been found out several biological components directly or indirectly relating to cancer metastasis. Further, antibodies to these components are constructed and somewhat effects are established on animal models of cancer metastasis. However, these antibodies have never been applied to humans hitherto. Although the currently available chemotherapeutics are efficacious against solid tumors, many of them exert only less effect on cancer metastasis than on cancer. Moreover, there is a problem that the development of drugs inhibiting the metastasis of cancer cells has made little progress. Under these circumstances, it has been urgently required to develop a drug which effectively inhibits the metastasis of cancer cells and improves the prognosis of a patient.
MIP-1α (Macrophage Inflammatory Protein-1α) is a molecule consisting of about 70 amino acids and belonging to the C—C chemokine family. It is released by activated lymphocytes, monocytes, etc. and induces the migration of dendritic cells, monocytes, Th1 cells and so on. MIP-1α is known as a ligand for CCR1 and CCR5 which are chemokine receptors expressed in immature dendritic cells (see, for example, Hideki Nakano, Saibo Kogaku, Vo. 19, No. 9, pp. 1304-1310 (2000)).
Also, there have been known functional derivatives of MIP-1α that are equivalent to biological activity of MIP-1α. In the case of MIP-1α, for example, a MIP-1α variant (hereinafter called eMIP or BB10010) in which Asp at the 26-position in MIP-1α is substituted by Ala and which is composed of 69 amino acids starting with Ser at the amino end is known. It is found out that this MIP-1α variant has a remarkably improved anticoagulant ability with an activity comparable to the wild type. And this variant has been investigated on improving leukopenia, which occurs as a side effect of chemotherapy for cancer (E. Marshall et al., European Journal of Cancer, Vol. 34, No. 7, pp. 1023-1029 (1998)).
It has been already known that neocarzinostatin chemically modified with a partially butyl-esterified styrene-maleic acid copolymer, which is an amphiphilic polymer, is usable as a carcinostatic agent (general name: zinostatin stimalamer) (Japanese Patent Publication of Examined Application No. 33119/1989). It is also known that, when administered into the blood, this drug accumulates almost selectively in a solid tumor and is sustained therein over a long period of time, i.e., showing the so-called EPR effect. Owing to these characteristics, it has been employed as a carcinostatic agent specifically targeting cancer. Also, a peptidic agonist chemically modified with an amphiphilic polymer and its functional derivative are known (WO 01/83548). Moreover, it is known that xanthine oxidase modified with polyethylene glycol shows the EPR effect on tumor cells (Japanese Patent Publication of Unexamined Application No. 060499/1999). In each of these cases, an antitumor effect is established by using a substance directly attacking against tumor cells. Namely, these methods aim at accumulating an aggressive substance selectively in a target site to thereby minimize the effects of the substance on normal cells or tissues.
It is also known that a protein modified with a polyethylene glycol derivative which is an amphiphilic polymer exhibits delayed clearance or lowered antigenicity in vivo (Yoshimoto et al., Jpn. J. Cancer Res., 77, 1264 (1986); Abuchowski et al., Cancer Biochem. Biophys., 7, 175 (1984); Japanese Patent Publication of Unexamined Application No. 178926/1986; Japanese Patent Publication of Unexamined Application No. 115820/1987; Domestic Re-publication of PCT international publication for patent application No. WO96/28475; Publication of Japanese translations of PCT international publication for patent application No. 513187/1999; Japanese Patent Publication of Unexamined Application No. 310600/1999, Publication of Japanese translations of PCT international publication for patent application No. 517304/2000). Furthermore, there are known interleukin-1, interleukin-6, interferon and so on each modified with polyethylene glycol (Japanese Patent Publication of Unexamined Application No. 117300/1993; Japanese Patent Publication of Unexamined Application No. 256394/1994; and Japanese Patent Publication of Unexamined Application No. 25298/1997).